Means for sterilizing liquid



Feb. 8, 1966 P. o. SKOLDBERG 3,233,964

MEANS FOR STERILIZING LIQUID Original Filed Feb. 8, 1955 Fig.2

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mede/ United States Patent 3,233,964 MEANS FOR STERILIZING LIQUID PerOlof Skoldberg, SaltsimDuvnas, Sweden, assignor to ,A. B. Purac, Lund,Sweden, a corporation of Sweden Continuation of application Ser. No.486,913, Feb. 8, 1955. This application Mar. 30, 1962, Ser. No. 193,348Claims priority, application Sweden, Feb. 12, 1954,

7 Claims. (CI. 21-61) This invention relates to a method and means forsterilizing liquids, i.e., for destroying or making otherwise inactivebacteria or other cellular organisms in liquids. 'It has been found thatgerms or bacteria in a liquid may be killed or at least renderedinactive by subjecting such liquid to pressure shocks of high amplitudeand short duration. However, the methods and means disclosed so far arenot suitable for handling large volumes of liquids which may becontaminated with impurities and which may be aggressive to the materialfrom which the shock treating apparatus is made.

This application is a continuation of my copending application SerialNo. 486,913 filed Feb. 8, 1955, and now abandoned.

One object of the present invention is to provide improved method andmeans for treatment of large quantities of liquid such as fresh water,waste water, milk or thelike. A further object of the invention is toprovide a method and means for continuously treating such liquids. Astill further object of the invention is to reduce the costs fortreating the liquids to a minimum. A still further object is to providean apparatus in which the parts subjected to destruction are cheap andeasily replaceable.

For these and other purposes I provide a process for sterilizing aliquid which comprises forcing a continuous stream'of said liquidthrough a chamber, and delivering shocks to the liquid in said chamberin the form of pressure pulses of high amplitude and short duration,suflicient to inactivate bacteria and small cellular organisms in theliquid. In a preferred form of the invention the shocks are delivered tothe fluid by a percussion apparatus including a free reciprocablepneumatic hammer piston. It has been found that the process according tothe invention is very suitable for treatment of fresh water, wastewater, milk, or the like. According to the intensity or duration of thetreatment the sterilization of the liquid may be carried on to anydesired degree of sterility or to full sterility so that a suitablereduction of the number of bacteria or other germs in the liquid isobtained.

The method and means according to the invention may also be used formedicinal purposes and the invention is particularly valuable inconnection with the sterilization of liquids which may not be heated ortreated with chemical means without undergoing a change of composition.The invention may also be used in connection with industrialfermentation or similar processes produced by micro organisms, forinstance, when it is desired to interrupt such fermentation or the likeat a certain stage.

One embodiment of an apparatus for carrying out the method according tothe invention together with a diagram is illustrated on the accompanyingdrawing. FIG. 1 illustrates diagrammatically the pressure variations ina liquid under treatment according to the invention. FIG. 2 illustratesdiagrammatically an apparatus for carrying out the method according tothe invention.

FIG. 1 illustrates diagrammatically how the pressure varies in a liquidwhich continuously flows through a chamber in which it is treated andthrough which the liquid is forced at a suitable preferably low feedpressure. The solid curve a in the diagram illustrates the variations ofthe pressure in the liquid as they may be assumed to 3,233,964 PatentedFeb. 8, 1966 'ice be when the liquid is subjected to pressure pulsesaccording to the invention. As obvious from FIG. 1 the pressure pulseshave an amplitude P which is high in comparison with the mean pressurePmedal of the liquid which is substantially the same as the feedpressure. It may occur that pressures below atmospheric also occur inthe liquid between the pressure pulses. However, the invention isindependent of the theoretical explanations which may be made to explainthe effect which the inventor has found, i.e., that bacteria and similarmicro organisms in a liquid may be killed or made inactive by continuousshock treatment of the liquid passing a hammering or shock treatmentchamber in which the hammering or shocks are produced by a free pistonpercussion apparatus, for instance a pneumatic or electric free pistonhammer having a suitable anvil block for transmitting the hammer blowsor shocks to the liquid in the chamber. It may be that the bacteria orthe like cannot stand the rapid repeated pressure raises or that thepressure reductions following thereon are the active part of thepressure pulses during the shock treatment or that the combination ofthe pressure raise and the pressure drop makes the bacteria inactive.

In FIG. 2 an apparatus is illustrated which is intended for continuoustreatment of liquids, such as waste water, with pressure pulsesaccording to the invention. The apparatus consists of a long tubularmember 1 forming a shock treatment chamber 32 and having a cover 2 atone end and a two-piece cover 3, 16 at the opposite end. The tubularmember 1 which in FIG. 2 has the central portion broken away is longrelatively to the diameter, for instance many times as long as thediameter. The chamber 32 communicates through an inlet 4 with a feedpump 31 capable of maintaining a suitable pressure in the chamber 32 andis provided with a restricted outlet 5. The apparatus may beincorporated in a fresh water system or a waste Water system or in amilk treating plant or other plant which contains a liquid which it isdesired to sterilize. The inlet 4 is placed in such a position and maybe shaped or arranged in such a way that the pressure pulses moving inthe liquid in the chamber 32 are substantially prevented from escapingthrough the inlet 4 towards the pump 31 which might otherwise be damagedby the pressure pulses. Similar arrangements may be provided in theoutlet when it is desired to connect the outlet to a closed conduitsystem. Special pressure wave filters similar to sound filters may beprovided in the inlet and outlet 4, 5 for this purpose. Preferably theinlet and outlet may be carried out valveless. In the illustratedembodiment the pressure pulses are to a certain degree prevented fromentering the inlet 4 or outlet 5 which are placed perpendicular to thedirection of travel of the pressure pulses in the chamber 32. In thehead 3, 16 an anvil block 6 is movable longitudinally of the chamber 32and fitted with a liquid tight sliding fit in a bore 7 in the headportion 3. The anvil block 6 may have a diameter which is substantiallythe same as the diameter of the chamber 32. In the illustratedembodiment the anvil block acts directly on the liquid in the chamber32, but is completely liquid tight against the percussion apparatus. Theanvil block has a flange 8 which is disposed between two disc typesprings 9 provided in an annular recess 10 in the head portion 16. Thesprings 9 serve to return the anvil block to the illustrated normalposition after each blow. Naturally, the springs 9 may be replaced byair cushions or a chamber under air pressure acting on a suitable pistonarea formed by the anvil block. The flange 8 might for this purpose beextended towards the cylindrical wall of the recess 10 to move as apiston in the recess 10, a compressed air conduit preferably withpressure regulator being connected between said flange and the head 3.The anvil and the chamber 32 by means of the pump 31.

block 6 has a shank portion 11 which extends into a cylinder 12 of apercussion motorwhich consists of the percussion motor is fitted betweenthe flange .34 of the tubular member 1 and the rear head 17 by means ofbolts 18. 35 indicates 'the main valve of-the percussion apparatus.

In operation of the apparatus according to the invention liquid to betreated is forced through the inlets In the chamber 32 the liquid issubjected to repeated shocks delivered by the percussion apparatusthrough the anvil block 6. In the illustrated embodiment the liquidflows against'the percussion waves. The velocity of the liquid streamthrough the chamber determines the time during which each particle oftheliquid is treated and-may be regulated according to the desireddegree of sterility of the liquid and leaving the chamber. The amplitudeP of the pressure pulses have varied in experiments carried out by theinventor between 1 and 500 kilogrammes/ square centimetre. Thetime-of-treatment has been varied betweenafew seconds up to an hour.Thefrequency of the percussion motor has been in the magnitude '10-50'-tude of the pressure pulses maybe selected according to experimentsfrom case to case. Sometimes the same result ma-ybe obtained with a highamplitude and a short treatment as with a low amplitude and a longertreatment. In order to makethe treatment effective the liquid should asfar as possible fill the chamber 32.- For this purpose the chamber ispreferably provided with a vent cock 30 at the top of the chamber.

The method and apparatus described hereinabove should only be consideredas an example and the invention may be varied in several ways within thescope of the claims. The pneumatic percussion apparatus illustrated inFIG. 2 may, for instance, be replaced by a combustion gas driven orelectrically driven percussion apparatus.

What I claim is:

1. In sterilizing apparatus for destroying andiinactivatingbacteriaand-other micro-organisms ina liquid by generating and propagatingpressure waves therein, the combination which comprises a straighttubular chamber-having an open liquid inlet and outlet, .purnp meansforcontinuously feeding liquid to be treated through said chamber by saidinlet and outlet thereof, and mechanical percussive impact pulsegenerating means at one end of said tubular chamber for generatingpulses longitudinally of said chamberfor propagation through said liquidtherein by direct impact on said liquid in said chamber, said pulsesbeing in therange of about 1 to 500 kg. per sq. cm. amplitude andhavingafrequency within theaudible range and well below 10,000 cyclesper second.

2. Apparatus as recited in claim 1 in which said mechanical percussionapparatus includes a piston in one end of said chamber and axiallyreciprocating withrespect thereto, and pneumatic percussion motor meansfor drivingsaid piston to impart said impact pulses to said liquid insaid chamber.

3. Apparatus as recited in claim 1 in which vent means are provided insaid tubular chamber for assuring ,the.

complete: filling'thereof with said liquid.

4. Apparatus as recited in claim 1 in which said inlet and said outletof said tubular chamber communicatetherewith through the longitudinalwallsthereof for inhibiting transmission of said longitudinally directedimpact pulses outwardly through said inlet-and said outlet.

5. *Apparatus'as recited in claim 1 in whichsaid liquid outlet has arestricted cross sectional area and in.which' said pump means maintainsa positive feedingv pressure on;

said-[liquid insaid tubular chamber against said restricted outlet.

I6. Apparatus as recited in claim 1 in which the lo'ngi-' theiaction oftudinal extent of said tubular chamber is substantially greater than thetransverse extent thereof for retaining ;a

quantity of said liquid continuously flowing therethrough. for asufficient time for subjecting said liquid to a sub-- sta'ntial numberofsaid impact :pulses propagated there-- References Cited by the ExaminerUNITED STATES PATENTS 2,138,839 12/1938 Chambers 992l7 2,219,348 10/1940 Turner 2'16l 2,585,103 2/1952. Fitzgerald 99--217 X FOREIGN PATENTS356,783 9/1931 Great "Britain.

A. LOUIS MONACELL, Primary Examiner. ABRAHAM H. WINKELSTEIN, Examiner.

1. IN STERLIZING APPARATUS FOR DESTROYING AND INACTIVATING BACTERIA ANDOTHER MICRO-ORGANISMS IN A LIQUID BY GENERATING AND PROPAGATING PRESSUREWAVES THEREIN, THE COMBINATION WHICH COMPRISES A STRAIGHT TUBULARCHAMBER HAVING AN OPEN LIQUID INLET AND OUTLET, PUMP MEANS FORCONTINUOUSLY FEEDING LIQUID TO BE TREATED THROUGH SAID CHAMBER BY SAIDINLET AND OUTLET THEREOF, AND MECHANICAL PERCUSSIVE IMPACT PULSEGENERATING MEANS AT ONE END OF SAID TUBULAR CHAMBER FOR GENERATINGPULSES LONGITUDINALLY OF SAID CHAMBER FOR PROPAGATION THROUGH SAIDLIQUID THEREIN BY DIRECT IMPACT ON SAID LIQUID IN SAID CHAMBER, SAIDPULSES BEING IN THE RANGE OF ABOUT 1 TO 500KG. PER SQ. CM. AMPLITUDE ANDHAVING A FREQUENCY WITHIN THE AUDIBLE RANGE AND WELL BELOW 10,000 CYCLESPER SECOND.